The present invention is related to an operational control method for a cylindrical crusher.
Most of blast furnace slag, convertor slag and electric furnace slag or the like produced in the processes of iron manufacture and steel manufacture had been disposed by throwing away. However, in recent years because of decrease of reclaimable land and in view of effective utilization of resources, recovery of an iron content from slag and reuse of the slag for aggregate etc. have been practiced. In this reason, by conducting such operations as a crushing process for rough breaking or deformation of massive furnace slag and then additional successive smashing process as well as sift sorting and magnetic separation procedures and the like, a concentrate whose iron content ratio is high is separated then withdrawn, and it is reused as a slag product and also an aggregate. In addition, in the crushing process of the rough breaking or deformation of the massive furnace slag a swingable type crushing apparatus (U.S. Pat. No. 4,637,562) or the like is utilized, while in the process of the pulverizing or grinding of the slag of a cylindrical crusher of a rod mill or the like is employed.
In such a way, the massive furnace slag whose dimension is greater than 300-500 mm and whose iron content ratio is about 50-60% is gradually decreased in size up to approximately 0-50 mm, and such a furnace slag as having the iron content ratio of 90-98% can be obtained.
The furnace slag is a non-uniform aggregation which is composed of melt iron and fused ore slag etc. When the slag is under the crushing operation, selective crushing proceeds in such a manner that the crushing is developed from the boundary portion or the like as the starting point where the iron content ratio is poor but ore slag content ratio is rich and the strength is low, thereby selectively crushing the furnace slag into one which has high strength and a rich iron content ratio and the other which has low strength and a poor iron content ratio. In this case, in the crushing process the crushing operation is performed in a crushing circuit where the supply means of the furnace slag and the cylindrical crusher is connected in series, and furnace slag of a certain dimensions is supplied to produce the furnace slag product with fine particle size. The particle size of this crushed product depends on the supplying amount from the supply means; the diameter and length of the cylindrical crusher; configuration, dimensions and fill-up quantity of media to be crushed; and the revolution speed of the cylindrical crusher and the like. In an ordinal operation, when the properties and dimension of the furnace slag are uniform, the particle size of the slag particularly depends on the supplying amount from the supply means and the revolution speed of the cylindrical crusher. The crushed product of the furnace slag produced under such operations is further subjected to the operations such as the sift sorting and the magnetic separation and so forth, whereby the ore slag is separated from the crushed product to be removed so that the furnace slag product which has high iron content ratio can be obtained.
However, in the operational control method by the conventional cylindrical crusher explained hereinbefore, there are such problems that since the particle size distribution and the iron content ratio of the furnace slag product is not detected directly and the supplying amount from the supply means and/or the revolution speed of the cylindrical crusher are not variable controlled by the control device, when the properties, the configuration and the dimensions of the furnace slag vary, the properties, the configuration and the dimensions of the furnace slag produce may change remarkably, so that the furnace slag which provides appropriate particle size distribution and iron content ratio can not be produced efficiently.
An object of the present invention is to resolve these conventional problems and to provide an improved operational control method for a cylindrical crusher which can sufficiently effectively produce a furnace product having appropriate particle size distribution and iron content ratio to the substantial fluctuation in the properties and configuration of the furnace slag, while variably controlling the supplying amount from the supply means and the revolution speed of the cylindrical crusher.